1. Field
Example embodiments relate to a semiconductor memory device. Other example embodiments relate to a non-volatile memory device including a metal-insulator transition (MIT) material.
2. Description of the Related Art
Of the semiconductor memory devices, non-volatile memory devices maintain stored data even when power is turned off.
The configuration of a memory cell, which is a basic element in a non-volatile memory device, differs depending on the field where the non-volatile memory device is used. A flash memory device is a type of non-volatile memory device.
FIG. 1 is a diagram illustrating a cross-sectional view of a conventional flash memory device.
Referring to FIG. 1, a source region 11 and a drain region 12 may be formed in a substrate 10. A gate stack 20 may be formed on the substrate 10 between the source region 11 and the drain region 12. The gate stack 20 may include a tunneling layer 30, a charge trap layer 40, a blocking layer 50 and a gate electrode 60.
In the conventional flash memory device, leakage of charges is prevented (or reduced) by blocking the charges using the tunneling layer 30 and the blocking layer 50. The tunneling layer 30 may be formed having a thickness of 5 nm to 10 nm. If the thickness of the tunneling layer 30 decreases, a charge storing speed increases. As such, the charge leakage may increase. As the charge storing speed increases, the retention characteristics of the memory device may decrease. If the thickness of the tunneling layer 30 increases, the retention characteristics may increase. A threshold voltage for a writing operation may also increase resulting in a reduced writing speed.